1
PHYS 187 Final Exam Questions with Correct
Answers | Updated (100% Correct Answers)
A star's luminosity is the
surface temperature of the star
lifetime of the star
total amount of light that the star radiates each second
total amount of light that the star will radiate over its entire lifetime apparent
brightness of the star in our sky Answer: total amount of light that the star
radiates each second
What is the approximate composition of the Sun?
50 percent hydrogen, 25 percent helium, 25 percent other elements
100 percent hydrogen and helium
70 percent hydrogen, 28 percent helium, 2 percent other elements
70 percent helium, 28 percent hydrogen, 2 percent other elements
98 percent hydrogen, 2 percent helium and other elements Answer: 70 percent
hydrogen, 28 percent helium, 2 percent other elements
Suppose you put two protons near each other. Because of the electromagnetic
force, the two protons will
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,2
remain stationary.
repel each other.
collide.
join together to form a nucleus.
attract each other. Answer: repel each other
The spectral sequence in order of decreasing temperature is
BAGFKMO.
OBAGFKM.
ABFGKMO.
OFBAGKM.
OBAFGKM. Answer: OBAFGKM
Why do astronomers often measure the visible-light apparent brightness instead
of the total apparent brightness of a star?
In order to measure the total apparent brightness of a star, you must measure its
brightness in all wavelengths, and this is difficult to do. The only wavelengths you
can measure from the surface of Earth are visible and radio wavelengths.
Most stars do not put out light in other ranges of the spectrum.
Astronomers are lazy.
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,3
they are identical for most stars.
All stars put out most of their light in the visible range of the spectrum. Answer:
In order to measure the total apparent brightness of a star, you must measure its
brightness in all wavelengths, and this is difficult to do. The only wavelengths you
can measure from the surface of Earth are visible and radio wavelengths.
Thermal radiation is defined as ________.
radiation with a spectrum whose shape depends only on the temperature of the
emitting object.
radiation produced by an extremely hot object.
radiation that is felt as heat.
radiation in the form of emission lines from an object. Answer: radiation with a
spectrum whose shape depends only on the temperature of the emitting object.
How does the explosion of a nuclear bomb provide evidence of the theory of
relativity?
The bomb causes things in its vicinity to move at very high speeds, allowing
scientists to measure effects of time dilation.
The mass of the bomb when it explodes is much greater than its normal mass.
The bomb shortens the lifetimes of all people who happen to be near it when it
detonates.
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, 4
The bomb produces energy in accord with E = mc2, which is part of the theory of
relativity. Answer: The bomb produces energy in accord with E = mc2, which is
part of the theory of relativity.
On a Hertzsprung-Russell diagram, where would we find red giant stars?
lower right
upper left
upper right
lower left Answer: upper right
Why do the predicted consequences of the special theory of relativity seem so
strange to most of us?
because they are self-contradictory, making it impossible to make any sense of
them
because they are obvious only at speeds that we never experience in our daily
lives
because they contradict the well-tested ideas of Newton's laws of motion
because they affect only subatomic particles and not big things like people
Answer: because they are obvious only at speeds that we never experience in
our daily lives
In the late 1800s, Kelvin and Helmholtz suggested that the Sun stayed hot thanks
to gravitational contraction. What was the major drawback of this idea?
© 2026 All rights reserved
PHYS 187 Final Exam Questions with Correct
Answers | Updated (100% Correct Answers)
A star's luminosity is the
surface temperature of the star
lifetime of the star
total amount of light that the star radiates each second
total amount of light that the star will radiate over its entire lifetime apparent
brightness of the star in our sky Answer: total amount of light that the star
radiates each second
What is the approximate composition of the Sun?
50 percent hydrogen, 25 percent helium, 25 percent other elements
100 percent hydrogen and helium
70 percent hydrogen, 28 percent helium, 2 percent other elements
70 percent helium, 28 percent hydrogen, 2 percent other elements
98 percent hydrogen, 2 percent helium and other elements Answer: 70 percent
hydrogen, 28 percent helium, 2 percent other elements
Suppose you put two protons near each other. Because of the electromagnetic
force, the two protons will
© 2026 All rights reserved
,2
remain stationary.
repel each other.
collide.
join together to form a nucleus.
attract each other. Answer: repel each other
The spectral sequence in order of decreasing temperature is
BAGFKMO.
OBAGFKM.
ABFGKMO.
OFBAGKM.
OBAFGKM. Answer: OBAFGKM
Why do astronomers often measure the visible-light apparent brightness instead
of the total apparent brightness of a star?
In order to measure the total apparent brightness of a star, you must measure its
brightness in all wavelengths, and this is difficult to do. The only wavelengths you
can measure from the surface of Earth are visible and radio wavelengths.
Most stars do not put out light in other ranges of the spectrum.
Astronomers are lazy.
© 2026 All rights reserved
,3
they are identical for most stars.
All stars put out most of their light in the visible range of the spectrum. Answer:
In order to measure the total apparent brightness of a star, you must measure its
brightness in all wavelengths, and this is difficult to do. The only wavelengths you
can measure from the surface of Earth are visible and radio wavelengths.
Thermal radiation is defined as ________.
radiation with a spectrum whose shape depends only on the temperature of the
emitting object.
radiation produced by an extremely hot object.
radiation that is felt as heat.
radiation in the form of emission lines from an object. Answer: radiation with a
spectrum whose shape depends only on the temperature of the emitting object.
How does the explosion of a nuclear bomb provide evidence of the theory of
relativity?
The bomb causes things in its vicinity to move at very high speeds, allowing
scientists to measure effects of time dilation.
The mass of the bomb when it explodes is much greater than its normal mass.
The bomb shortens the lifetimes of all people who happen to be near it when it
detonates.
© 2026 All rights reserved
, 4
The bomb produces energy in accord with E = mc2, which is part of the theory of
relativity. Answer: The bomb produces energy in accord with E = mc2, which is
part of the theory of relativity.
On a Hertzsprung-Russell diagram, where would we find red giant stars?
lower right
upper left
upper right
lower left Answer: upper right
Why do the predicted consequences of the special theory of relativity seem so
strange to most of us?
because they are self-contradictory, making it impossible to make any sense of
them
because they are obvious only at speeds that we never experience in our daily
lives
because they contradict the well-tested ideas of Newton's laws of motion
because they affect only subatomic particles and not big things like people
Answer: because they are obvious only at speeds that we never experience in
our daily lives
In the late 1800s, Kelvin and Helmholtz suggested that the Sun stayed hot thanks
to gravitational contraction. What was the major drawback of this idea?
© 2026 All rights reserved
